FULL PRODUCT VERSION :


A DESCRIPTION OF THE PROBLEM :
change size from content in tab
(add column / row zo gridPane)
dont update size from TabPane

onle add new Tab / switch to other triggers layout change


REGRESSION. Last worked in version 8u66

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
add Tab ([add Tab])
add Labels to Tab ([add Label])

-> add new Tab or switch to other Tab
-> TabPane change Width


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class TabPaneLayoutMain extends Application {

    private static final double MAX_VALUE = Double.MAX_VALUE;
    private static final double USE_PREF_SIZE = Double.NEGATIVE_INFINITY;
    private static final double USE_COMPUTED_SIZE = -1.0;

    /**
     * @param args
     */
    public static void main(String[] args) {
        launch(TabPaneLayoutMain.class, args);
    }

    @Override
    public void start(final Stage stage) throws Exception {
        final BorderPane root = new BorderPane();

        final TabPane tabs = new TabPane();
        tabs.setMinSize(USE_PREF_SIZE, USE_PREF_SIZE);
        tabs.setPrefSize(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE);
        tabs.setMaxSize(USE_PREF_SIZE, USE_PREF_SIZE);
        BorderPane.setAlignment(tabs, Pos.TOP_LEFT);
        
        final Button add = new Button("add Tab");
        root.setTop(add);
        add.setOnAction((event) -> tabs.getTabs().add(new AddTab()));

        root.setCenter(tabs);
        stage.setScene(new Scene(root, 800, 800));
        stage.show();
    }

    private static final void changeTabPaneSize(final TabPane tabPane) {
        final int index = tabPane.getSelectionModel().getSelectedIndex();
        if (index < 0 || tabPane.getTabs().isEmpty()) {
            return;
        }

        if (tabPane.getTabs().size() == 1) {
            final Tab tab = tabPane.getTabs().remove(0);
            tabPane.getTabs().add(tab);
        } else if (tabPane.getTabs().size() > 1 && index == 0) {
            tabPane.getSelectionModel().select(1);
        } else if (tabPane.getTabs().size() > 1 && index != 0) {
            tabPane.getSelectionModel().select(1);
        }

        tabPane.getSelectionModel().select(index);
    }

    private final class AddTab extends Tab {
        private final int[] column;
        private final GridPane grid;

        private AddTab() {
            super(String.valueOf(System.currentTimeMillis()));

            this.column = new int[]{0};

            this.grid = new GridPane();
            this.grid.setHgap(4);
            this.grid.setVgap(4);
            
            this.grid.setMinSize(USE_PREF_SIZE, USE_PREF_SIZE);
            this.grid.setPrefSize(USE_COMPUTED_SIZE, USE_COMPUTED_SIZE);
            this.grid.setMaxSize(USE_PREF_SIZE, USE_PREF_SIZE);

            this.grid.getRowConstraints().add(new RowConstraints(USE_PREF_SIZE, USE_COMPUTED_SIZE, USE_PREF_SIZE));

            final Button add = new Button("add Label");
            add.setOnAction((event) -> add(new Label("label")));
            add(add);

            setContent(this.grid);
        }

        private final void add(final Node node) {
            GridPane.setConstraints(node, this.column[0]++, 0);
            this.grid.getChildren().add(node);
            this.grid.getColumnConstraints().add(new ColumnConstraints(USE_PREF_SIZE, USE_COMPUTED_SIZE, USE_PREF_SIZE));

            if (getTabPane() != null) {
                // workaround
                // changeTabPaneSize(getTabPane());
            }
        }
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
    private static final void changeTabPaneSize(final TabPane tabPane) {
        final int index = tabPane.getSelectionModel().getSelectedIndex();
        if (index < 0 || tabPane.getTabs().isEmpty()) {
            return;
        }

        if (tabPane.getTabs().size() == 1) {
            final Tab tab = tabPane.getTabs().remove(0);
            tabPane.getTabs().add(tab);
        } else if (tabPane.getTabs().size() > 1 && index == 0) {
            tabPane.getSelectionModel().select(1);
        } else if (tabPane.getTabs().size() > 1 && index != 0) {
            tabPane.getSelectionModel().select(1);
        }

        tabPane.getSelectionModel().select(index);
    }